SPIDERS. 179 



CADDICE-FLIES. 



On account of their curious appearance and habits, 

 these insects are the most interesting while in the larva 

 state. They live at the bottom of ponds and streams, 



Fig. 339. Caddice-FIy. 



in cases which they construct of bits of wood, or grasses, 

 or of grains of sand, or of fragments of broken shells, 

 and which are lined with silk, which they spin from 

 their mouths. They sometimes load one side of the 

 case with heavier pieces, in order to keep that side 

 downward. 



SPIDERS, OR ARACHNIDS. 



Spiders have the body divided into only two well- 

 marked portions, the head and the hind body. They 

 have eight legs, and two palpi or feelers resembling 

 legs, but no wings, and they do not change their form 

 in passing from the young to the adult state. Most 

 kinds feed upon insects. 



True Spiders have, at the hind part of their body, a 

 most wonderful organ, called the spinneret, by which 

 the delicate threads of the spider-web are spun. It 

 consists of four to six knobs, with a thousand or more 

 holes in each knob. Through these the invisible silken 

 threads pass out, more than four thousand at a time, 

 and at a little distance from the knobs all these 



